The invention relates to a contactless and batteryless chip card having an antenna coil, a transmission and reception stage, which via an alternating field generated by a write/read unit supplies the chip with energy and insures bidirectional data transmission to the write/read unit, and a functional circuit part which is dependent on the respective application of the chip card.
Chip cards of this type are known from, for example, Winfried Wigand "Die Karte mit dem Chip", Siemens Nixdorf Informationssysteme AG, Berlin and Munich, 1991, in particular pages 34-36. In known contactless and batteryless chip cards, the current is supplied by, for example, transformer connection via an alternating field generated by an associated write/read unit. Data transmission too, from and to the chip card, is achieved by modulation of this alternating field. Certain functions of the chip card, such as the programming of EEPROM cells with data transmitted via the field to the chip card, require a higher energy quantity than other functions of the card, such as transmission and reception of data. These energy-consuming functions are only implemented defectively and incompletely when the current supply is deficient. For example, data preservation cannot be ensured during programming of the EEPROM cells of the chip card unless sufficient current is supplied to the chip card. Since the current supply of the chip card is dependent on the distance from the write/read unit and its transmission capacity besides other factors, a change in the distance between the chip card and the write/read unit may have the effect that those chip card functions requiring a higher quantity of energy for their implementation are not implemented properly.